BIOC40H3 Lecture Notes - Lignin, Vessel Element, Water Vapor
Document Summary
As we discussed in the last lecture on water and plants, there is an inherent conflict between a plant"s need to take in co2 for photosynthesis and to conserve water. This is because both co2 and water must use the same pathway through stomates, with. Co2 going in, and water being lost out of the pores. Water potential ( ) of soils can be divided into three components osmotic pressure ( ) hydrostatic pressure ( : gravitational potential ( ) Since solute concentration in soil tends to be very low, the osmotic pressure ) is generally negligible. For wet soils the hydrostatic pressure ( ) is very close zero, but as soil dries out, the hydrostatic pressure decreases and becomes negative. Remember that water has a high surface tension that tends to decrease air-water interfaces, but because of high adhesive forces in water, it also clings to the surfaces of soil particles.